Wallboard is the material of choice in the construction and renovation of homes and buildings today. Wallboard is prefabricated in sections and shipped to construction sites where it is joined together to form interior walls and partitions. Corner bead is used to bind edges of wallboard together at outwardly projected corners. The corner bead, a pre-made metallic beading, is sold commercially in lengths of 8 and 10 feet with an included angle of 90.degree. and lengths of 10 feet with an included angle of 135.degree.. Integral with the bead of the corner bead are a pair of wings extending the length of the bead and generally forming an included 90.degree. angle therebetween. Each of the Wings is provided with a plurality of pre-punched holes extending along the entire length. The purpose of these holes is to permit finishing compound to flow therein once the corner bead is installed to an outer corner by nailing.
The corner bead is generally made with an included angle of 90.degree. between the two outwardly extending wings which is appropriate for a standard 90.degree.outside corner. However, many architectural plans require a wall with an excluded angle of 225.degree. requiring a corner bead with wings having an included angle of 135.degree. and complementary corners having included angles of 135.degree..
As a result of the need for dry wall corner bead having an included angle of 135.degree., wallboard installers have resorted to various means of increasing the included angle between corner bead wings. For example, a crude practice is to place a length of corner bead on a cement floor with the wings facing upwardly and then by using a hammer between the wings increasing the angle therebetween. As a result of this and other methods which are employed, the corner bead becomes badly bent and kinked and subjecting the installer to potential injury from the unbound wing edges.
In construction situations requiring the larger included angle corner bead and having ceiling heights of 10 feet, the 135.degree. corner bead must be spliced together since it is available only in lengths of 8 feet. The instant invention however will allow commercially available lengths of 10'-90.degree. corner bead to be used without splicing once it has been modified with the apparatus taught by this invention.
A stationary device which increases the angle between the extended wings of a corner bead is shown in U.S. Pat. No. 4,848,126, comprising a stationary support having a V-groove for positioning the bead and movable pressure applying spreading means, in the shape of a ball supported by an axle rotatably secured to a yoke which is movable perpendicular to the length of the corner bead for varying the angle of the wings. The principal disadvantages are that the device is stationary--its design limits it use to a fixed location at a construction site, it is not easily used as it requires several adjustments and cannot be operated quickly.